Method of stabilization of rubber with a substituted triazine and compositions stabilized thereby



United States Patent METHOD OF STABILIZATION 0F RUBBER WITH ASUBSTITUTED TRIAZINE AND COMPOSI- TIONS STABILIZED THEREBY MartinDexter, White Plains, Martin Knell, Stillwater Hills, Ossining, and EricA. Ruskin, Bronx, N.Y., assignors to Geigy Chemical Corporation,Ardsley, N.Y., a corporation of Delaware No Drawing. Originalapplication Apr. 11, 1961, Ser. No. 99,663. Divided and this applicationOct. 25, 1962, Ser. No. 242,571

3 Claims. (Cl. 260-453) This application is a divisional application ofcopending application Serial No. 99,663, filed April 11, 1961, nowabandoned. Application Serial No. 99,663 is in turn acontinuation-in-part of copending application Serial No. 21,604, filedon'April 12, 1960; now abandoned, and also a continuation-impart ofcopending application Serial No. 87,521, filed February 21, 1961, nowabandoned.

This invention relates to a method of stabilization of rubber with asubstituted triazine and to compositions stabilized thereby.

In one aspect of-the invention, rubber is stabilized with compounds ofthe formula:

In this aspect of the invention, rubber is stabilized preferably withcompounds of the general formula:

wherein R and R each independently represents alkyl having from 1 to 18carbon atoms, e.g., methyl, ethyl, propyl,

butyl, octyl, dodecyl, octadecyl, etc.,

R rep-resents a'lkylhydroxyphenyl, preferably having from 7 to 24 carbonatoms, e.g., methylhydroxyphenyl, ethylhydroxyphenyl,propylhydr-oxyphenyl, butyl'hydroxyphenyl, octylhydroxypheny-l,dodecylhydroxyphenyl, octadecylhydroxyphenyl, dimethylhydroxy- In thisspecification, the term lower alkyl signifies an alkyl group having from1 to 6 carbon atoms, and aryl embraces within its meaning not merelycarbocyclic, e.g., phenyl, naphthyl, etc., but also heterocyclicradicals, e.g., pyri-dyl, thiazolyl, etc.

Up to the present time, the'use of the substituted triazines of theinvention in stabilizing rubber, e.g. artifical rubber, such aspolyisoprene or styrene-butadiene rubber, has not been known. It has nowsurprisingly been found that such materials are stabilized, e.g.,against oxidative deterioration, by incorporating therein effectivequantities of one of the substituted triazines defined according to thepresent invention.

Accordingly, it is a prime object of the invention to provide stablerubber, preferably stable artificial rubber, e.g., polyisoprene. Otherexamples of rubber stabilized according to the invention includestyrene-butadiene rubber,

polybutadiene rubber, butyl rubber, nit-rile rubber, neoprene rubber andnatural rubber alone, blends of artificial rubber and natural rubber,such as e.g. natural rubber and polybutadiene rubber. In fact, anyrubber subject to degradation by atmospheric oxygen is within the scopeof the present invention. Artificial rubber, however, is preferred.

It is a further object of the invention to provide a method forstabilizing rubber, particularly artificial rubber and blends thereofwith natural rubber, by incorporating in said rubber a stabilizingamount of a triazine compound according to the invention.

. and solubility are also important factors.

-It is understood that the stabilizers of the invention are notnecessarily of equivalent potency. The specific stabilizer most usefulto a given unstable rubber will dependupon several factors for itsadvantages. Availability and cost of raw materials for the manufactureof the stabilizer and effective inhibitory action of the stabilizer,including duration and degree of activity, are among the factors whichcontrol the choice of a specific stabilizer for a specific rubbersubstrate which is normally subject to deterioration. Toxicity, color,stability to light and/ or heat For example, a preferred compositionaccording to the invention comprises from about 0.001% to about 5% byweight of 6-(4- hydroxy 3,5-di-t-butylanilino) 2,4-bis-(n-octylthio)-1,3,5-triazine and polyisop-rene.

In general, stabilizers of the invention are employed in a concentrationof from about 0.001% to about 5% by weight, preferably from about 0.01%to about 1% by weight. The specific concentration used varies with theunstabilized rubber substrate and the specific stabilizer, as notedabove. When mixtures of two or more stabilizers are employed in rubber,usually the total amount of added stabilizers will not exceed 10% of thetotal stabilized rubber.

When the triazine stabilizers disclosed herein are used to stabilizerubber in combination with other additive agents, it is contemplated.that there may be added, for example, antioxidants, carbon black,accelerators and other chemicals used in rubber compounding,plasticizers, color stabilizers, heat stabilizers, UV absorbers, dyesand pigments, etc. I

The compounds of the present invention are advantageously prepared, forexample, according to the following reactions, wherein R represents thesame or different 3 radicals as defined hereinbelow (the said R radicalscorresponding to the previously mentioned R R R etc.):

(A) ITTHR lTlI-[R DITHR (Ill IITHR IITHR RSH N RHN I N/\\I RSH (D) NHRITTHR N N Cl-iqqJ-Cl 2ROH ROflN JOR In the foregoing scheme ofreactions, it is understood that, While cyanuric chloride is a preferredstarting material, other triazine compounds having reactive groups otherthan halogen may be used. Likewise, any combination of the methodsoutlined in A, B, C, D, and B may be employed to attain the desiredvariant compound within the scope of the invention.

In the foregoing scheme also, the H of ROH and RSH may be replaced by asuitable reactive group or atom, as e.g. an alkali metal, such assodium, potassium, etc., or the ammonium radical. In the case of theimino group, hydrogen may be replaced by alkyl, benzyl, etc. Also, Xrepresents halogen, e.g., chlorine.

For reaction with a suitable triazine, the amines, mercaptans andhalides of the formulae RNH RSH and RX are useful. The halide may be anysuitable halide, as e.g. a fluoride, iodide, bromide and, preferably, achloride. The R group is advantageously an alkyl group having from 1 to18 carbon atoms, e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl,heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl,pentadecyl, hexadecyl, heptadecyl, and octadecyl. R is alsoadvantageously a cycloalkyl group, e.g., cyclopentyl and cyclohexyl. Inother aspects R is aryl, e.g., phenyl, hydroxyaryl, e.g. hydroxyphenyl,alkylaryl, e.g., alkylphenyl having from 7 to 24 carbon atoms, such astolyl, ethylphenyl, propyphenyl, butylphenyl, octylphenyl,octadecylphenyl, etc.; alkylhydroxyaryl, e.g. alkylhydroxyphenyl, suchas methylhydroxyphenyl, dimethylhydroxyphenyl, trimethylhydroxyphenyl,tetramethylhydroxyphenyl,. ethylhydroxyphenyl, diethylhydroxyphenyl,triethylhydroxyphenyl, tetraethylhydroxyphenyl, propylhydroxyphenyl,dipropylhydroxyphenyl, butylhydroxyphenyl, dibutylhydroxyphenyl,ootylhydroxyphenyl, dioctylhydroxyphenyl, octadecylhydroxyphenyl, etc.

Another useful class of R groups comprises the alkylthioalkyls, such asmethylthiomethyl, methylthioethyl, methylthiopropyl, methylthiobutyl,methylthiopentyl, etc. also ethylthiopentyl, etc., propylthiomethyl,'propylthioethyl, propylthiopropyl, propylthiobutyl, propylthiopentyl,etc., butylthiomethyl, butylthioethyl, butylthiopropyl, butylthiobutyl,butylthiopentyl, etc., pentylthiomethyl, pentylthioethyl,pentylthiopropyl, et-c., hexylthiomethyl, hexylthioethyl,hexylthiopropyl, etc., heptylthiomethyl, he-ptylthioethyl,hepthylthiopr-opyl, octylthiomethyl, octylthioethyl, etc.

Other useful R groups comprise benzyl, hydroxybenzyl andalkylhydroxybenzyl, e.g. methylhydroxybenzyl, ethylhydroxybenzyl,propylhydroxybenzyl, 'butylhydroxybenzyl, octylhydroxybenzyl, etc.;cyanoalkyl, e.g. cyanomethyl, cyanoethyl, cyanopropyl, cyanobutyl,cyanopentyl, cyanohexyl, etc.; carbalkoxyalkyl, e.g. carbomethoxymethyl,carbethoxyethyl, carbopropoxyethyl, carbododecanoxyethyl, etc.;carbalkoxyphenyl, e.g. carbomethoxyphenyl, carbethoxyphenyl,ca'rbopropoxyphenyl, carbododecanoxyphenyl, etc.

The following examples are illustrative of the invention, but by nomeans is the invention limited thereto. In all examples parts are byweight unless otherwise noted, and the relationship between parts byweight and parts by volume is as that of grams to cubic centimeters. Thetemperature is in degrees Centigrade.

' Example 1.6-(4-hydr0xy-3,S-di-t-butylanilino)2,4-

bis-(n-octylthio) -1,3,5-triazine (a)4-nitroso-2,6-di-t-butylphen0l.-750 parts by volume of ethanol,-cooledto are saturated with hydrogen chloride gas and then diluted'by theaddition of 4000 parts by volume of ethanol. 2,6-di-t-butylphenol (824parts) is dissolved in the alcoholic solution and a solution of sodiumnitrite (304 parts in 400 parts by I volume of water) is added at 15-20"over a period of one hour while stirring. Stirring is continued foranother 2 hours while allowing the temperature to rise to roomtemperature. 2000 parts by volume of water are added and the product isthen separated 'by filtration and washed well with water. The filtercake is slurried in 3000 parts by volume of petroleum ether, filtered,washed on the filter with 1000 parts by volume of petroleum ether anddried in a vacuum oven at 70-80". The yield of 4- nitroso-2,6-di-tbutylphenol, melting at 219, is 848 parts (90.2%

(b) 4-amin0-2,6-di-t-butylphenol.4 nitroso-2,6-di-tbutylphenol (176parts) is dissolved in 600 parts by volume of 5 N sodium hydroxide and1200 parts by volume of water, and a solution of sodium hydrosulfite(522 parts) in 2200 parts by volume of water is added with moderatespeed (about 30 minutes), during which time the temperature rises to53". After the addition is completed, stirring is continued for 2 /2hours after which the product is filtered rapidly, washed with 4000parts by volume of water and dried in a. vacuum desiccator overphosphoric anhydride. The yield of 4-amino-2,6-di-tbutylphenol, meltingat l05108 is 162.3 parts (98.5%).

(c) 6 (4 hydroxy-iS-di-t-butylanilino)-2,4-aichloro- 1,3,5-triazine.-Asolution of cyanuric chloride (18.4 parts) in boiling acetone parts byvolume) is poured in a thin stream while stirring into 200 parts byvolume of ice-water, keeping the temperature at 05 with externalcooling. 4-amino-2,6-di-t-butylphenol (22.1 parts) and sodium carbonate(5.3 parts) are added and the reaction mixture is stirred vigorouslyat'8-10 for 45 minutes. The mixture is then diluted by the addition of100 parts by volume of acetone and stirring is continued for anadditional hour at 8-10". The suspension is then poured into 500 partsby volume of ice-water, the precipitate is filtered off and dried invacuo. The yield of 6-(4-.hydroxy-3,5-di-t-butylanilino)-2,4-dichloro-1,3,5 triazine is 34.8 parts(94%). The product melts at 144.

(d) 6 (4 hydroxy 3,5 di t butylanilino) 2,4-bis-(n-octylthio)-1,3,5-triazine.An alcoholic solution of sodiumn-octylmercaptide (prepared by dissolving 2.3 parts of sodium in 50parts by volume of ethanol and adding 14.6 parts of n-octylmercaptan) isadded rapidly with stirring to a solution of 18.5 parts of6-(4-hydroxy-3,5-dit-butylanilino)-2,4-dichloro-1,3,5-triazine in 150parts by volume of ethanol. The reaction mixture is stirred and refluxedfor 1 /2 hours. After cooling to room temperature, 500 parts by volumeof water are added. The precipitated product is separated by filtrationand washed well with water. Purification of the product is accomplished'by dissolving in 300 parts by volume of boiling ethanol, addingactivated carbon, filtering and slowly recrystallizing. The 6(4-hydroxy-3,S-di-t-butylanilino)-2,4-bis-(n-octylthio)-1,3,5-triazine,which crystallizes as white needles, is filtered off, Washed with coldethanol and is dried in vacuo yielding 10.6 parts melting at 92-95Additional 8.6 parts having the same melting point are obtained byconcentration of the mother liquor. The total yield is 65.5% of thetheoretical yield.

Example 2.6-(N-acetyl-4-hydr0xy-3,5-di-t-butylanilino)2,4-bis-(n-0ctylthio)-1,3,5-triazine 23.5 parts of6-(4-hydroxy-3,S-di-t-butylanilino)-2,4-bis-(n-octylthio)-1,3,5-triazine and 200 parts by volume of aceticanhydride are heated at for 2 /2 hours, after which the volatilematerials are stripped from the reaction mixture under high vacuum (0.05mm. Hg) at water bath temperature. The viscous lemon colored liquidwhich remains in the distillation pot is dissolved in parts by volume ofether, washed with 10% (by weight) sodium bicarbonate solution, and thenwashed with water and finally dried over anhydrous magnesium sulfate.Thereafter, the ether is removed by evaporation on the steam bath andthe residue is finally stripped at 130 and 0.05 mm. Hg. The so-obtainedproduct weighs 22.5 parts. This product,6-(N-acetyl-4-hydroXy-3,S-di-tbutylanilino)-2,4-bis-(n-octylthio)-1,3,5-triazine,has the following analysis Calculated for C H N O S 2 C, Found: C,66.52%; H, 9.09%; N, 8.99%.

If in Example 2, valeric anhydride is substituted for acetic anhydride,then 6-(N-valeroyl-4-hydroxy-3,5-di-tbutylanilino)-2,4-bis-(n-octylthio)1,3,5 triazine is ob tained.

Further, if in Example 2, lauric anhydride is substituted foracetic'anhydride, then6-(N-lauroyl-4-hydroxy-3,5-dit-butylanilino)-2,4-bis-(n-octylthio)-1,3,5triazine is obtained.

7 Example 3 Stablized rubber is prepare-d by mixing in the cold:

, Parts Hevea latex crepe 100.0 Stearic acid 1.5 Zinc oxide a. 5.0

Diphenylguanidine 1.0 Sulfur 2.5

6-(4-hydroxy-3,S-di-t-butylanilino) 2,4 bis (noctylthio)-1,3,5-triazine1.0

The resultant mixture is vulcanized at 140 and tested according to ASTMD-l206-52T. The time required to elongate a test strip from 120 mm. to170 mm. is 10 hours for the unstabilized rubber and 17 hours for thestabilized rubber. In a similar way, styrene-butadiene rubber isstabilized. In a similar Way also, a blend of natural rubber (50 parts)and polybutadiene rubber (50 parts) is stabilized.

In like manner as in the foregoing Example 3, stable compositions ofnatural rubber are prepared having 0.9% by weight of the followingcompounds:

6-(4-hydroxy-3,5-di-t-butylanilino-N-acetyl)-2,4-bis-(noctylthio)-1,3,5-triazine(Ex. 2)

6-(N-valeroyl-4-hydroxy-3,5-di-t-butylanilino)-2,4-bis-(noctylthio)-1,3,5-triazine(Ex. 2)

6- (N-lauroy1-4-hydroxy-3,S-di-t-butylanilino) -2,4-bis-(noctylthio)-l,3,5-triazine (Ex. 2)

What is claimed is:

1. Method of stabilizing rubberv selected from the group consisting ofconjugated diene rubber, butyl rubber and nitrile rubber which comprisesincorporating therein a wherein R and R are each an alkyl group havingfrom 1 to 18 carbon atoms;

R is an alkylhydroxyphenyl group;

R is alkanoyl having from 1 to 12 carbon atoms;

and X and Yare each independently selected from the group consisting ofS, O and NR.;, Wherein R is aralkyl.

2. Stabilized composition of matter which comprises rubber selected fromthe group consisting of conjugated diene rubber, butyl rubber andnitrile rubber and a stabilizing amount of a stabilizer as defined inclaim 1.

3. Stabilized composition of matter which comprises rubber selected fromthe group consisting of conjugated diene rubber, butyl rubber andnitrile rubber and from about 0.001% to about 5% by Weight of astabilizer as defined in claim 1.

No references cited.

LEON J. BERCOVITZ, Prim ary Exariner.

H. E. TAYLOR, ]R., Assistant Examiner.

1. METHOD OF STABILIZING RUBBER SELECTED FROM THE GROUP CONSISTING OFCONJUGATED DIENE RUBBER, BUTYL RUBBER AND NITRILE RUBBER WHICH COMPRISESINCORPORATING THEREIN A STABILIZING AMOUNT OF A STABILIZER, SAIDSTABILIZER BEING A COMPOUND OF THE FORMULA